Perfluoroalkyleneethertriazine oligomer and process for producing the same

ABSTRACT

Perfluoroalkyleneethertriazine oligomer obtained by reacting a dinitrile compound NC--Ff 0  --CN, where Ff 0  is --(CFXOCF 2 )a(CF 2 )b(CF 2  OCFX)c--, where X is a fluorine atom or a CF 3  group, a is an integer of 1 to 5, b is an integer of 1 to 2 and c is an integer of 1 to 5, or Rf 0  is --CF 2  O(CF 2  O)dCF 2  --, where d is an integer of 1 to 8, with ammonia, further reacting the resulting diamizine compound with a dinitrile compound NC--Rf 1  --CN, Rf 1  has the same meaning as that for Rf 0  or Rf 1  is a perfluoroalkylene group having 4 to 8 carbon atoms thereby obtaining a perfluoroalkyleneetherpolyimidoylamizine oligomer, then reacting the resulting oligomer with a perfluoronitrile compound Rf 2  CN, Rf 2  is CF 3  (OCF 2 ) e  -- where e is an integer of 3 to 10 thereby treating the terminal groups thereof, and then subjecting the resulting terminal-treated oligomer to a ring-closing reaction with a perfluoroacylating agent RF 3  COY, Rf 3  is CF 3  (OCF 2 ) f  -- where f is an integer of 3 to 10 has a good resistance to oxidation in the presence of a metal at a high temperature, and can improve the heat resistance of a perfluoropolyetherpolytetrafluoroethylene powder-based grease, when added therto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a perfluoroalkyleneethertriazineoligomer and a process for producing the same, and more particularly anoily perfluoroalkyleneethertriazine oligomer useful as an effectiveoxidation stabilizer for greases, vacuum pump oils, etc. and a processfor producing the same.

2. Description of the Prior Art

Liquid perfluoropolyether has a good resistance to heat and oxidation,and also has good lubricability and non-flammability. However, itundergoes a thermal oxidation-type decomposition at a temperature of250° C. or higher, where the decomposition is accelerated in thepresence of some metal or oxide thereof, and the resulting decompositionproduct gives rise to metal corrosion.

The resistance of liquid perfluoropolyether to oxidation in the presenceof such a metal at a high temperature can be increased with an additivecapable of inhibiting progress of metal corrosion process. It is alsoknown that a good result can be obtained by using an aromatic phosphineand a phosphorus-containing triazine as oxidation-resistant,corrosion-resistant additives. However, these additives still havedrawbacks, i.e. a relatively large volatility at a high temperature anda low solubility in perfluoropolyether at room temperature or a lowertemperature.

Another class of liquids particularly stable for the thermal oxidationincludes a liquid perfluorotriazine. A fluorine-containing, symmetrictriazine has a high stability against the thermal oxidation even at 343°C., but undergoes complete evaporation at 204° C. over 6.5 hours due tothe low molecular weight. It is also known that α,ω-di(symmetrictriazinyl)perfluoroalkanes having various structures have a goodstability against the thermal oxidation, but undergo considerableevaporation at a higher temperature than 200° C. also due to arelatively low molecular weights, and thus have not yet been utilized asa lubricant additive or in other applications.

SUMMARY OF THE INVENTION

An object of the present invention is to provide aperfluoroalkyleneethertriazine oligomer having a good resistance tooxidation in the presence of a metal at a high temperature and capableof improving the heat resistance of perfluoropolyether-based oil orperfluoropolyetherpolytetrafluoroethylene powder-based grease, whenadded thereto.

According to the present invention, there is provided aperfluoroalkyleneethertriazine oligomer represented by the followinggeneral formula: ##STR1## wherein Rf⁰ is --(CFXOCF₂)a(CF₂)b(CF₂OCFX)c--, where X is a fluorine atom or a CF₃ group, a is an integer of1 to 5, b is an integer of 1 to 2 and c is an integer of 1 to 5, or Rf⁰is --CF₂ O (CF₂ O)dCF₂ --, where d is an integer of 1 to 8; Rf¹ has thesame meaning as that for Rf⁰ or a perfluoroalkylene group having 4 to 8carbon atoms; Rf² is a perfluoroalkyl group having 1 to 8 carbon atoms,CF₃ (OCF₂)e--, where e is an integer of 3 to 10, or RfO(CFXCF₂ O)kCFX--,where Rf is a perfluoro(lower alkyl) group, X is a fluorine atom or aCF₃ group, and k is an integer of 1 to 8; and Rf³ is Rf(OCFX)f--, whereRf is a perfluoroalkyl group having 1 to 8 carbon atoms, X is a fluorineatom or a CF₃ group, and f is an integer of 3 to 10, and n is 0.01 to 10and m is 0.01 to 20.

The present perfluoroalkyleneethertriazine oligomer can be producedaccording to a series of the following steps, where Rf⁰, Rf², Rf³, Rf³and n and m in the general formula for starting materials andintermediate products have the same meanings as defined above.

First step

Dinitrile compound represented by the general formula NC--Rf⁰ --CN issubjected to reaction with ammonia to obtain a diamizine compound I!represented by the following general formula: ##STR2##

Dinitrile compound for use in the present invention includes compoundsV! whose Rf⁰ is --(CFXOCF₂)a(CF₂)b (CF₂ OCFX)c--, for example, NCCF₂OCF₂ CF₂ CF₂ OCF₂ CN, NCCF₂ OCF₂ CF₂ CF₂ CF₂ OCF₂ CN, NCCF(CF₃)OCF₂ CF₂CF₂ OCF(CF₃)CN, NC CF(CF₃)OCF₂ !₂ CF₂ CF₂ OCF(CF₃)CN, NC CF(CF₃)OCF₂ !₂CF₂ CF₂ OCF(CF₃)!₂ CN and NC CF(CF₃)OCF₂ !₂ CF₂ CF₂ OCF(CF₃)!₂ CN₂, andcompounds VI! whose Rf⁰ is --CF₂ O(CF₂ O)dCF₂ --, for example, NCCF₂OCF₂ OCF₂ CN, NCCF₂ O(CF₂ O)₃ CF₂ CN, NCCF₂ O(CF₂ O)₆ CF₂ CN and NCCF₂O(CF₂ O)₈ CF₂ CN.

Among the compounds V!, compounds whose X is CF₃ can be produced byreacting the terminal groups of hexafluoropropeneoxide oligomer withalcohol to esterify the terminal groups, followed by reaction withammonia, or by direct reaction of the terminal groups with ammonia toform an acid amide H₂ NOCRf⁰ CONH₂, followed by dehydration reactionwith a dehydrating agent such as phosphoric anhydride, perfluoroaceticanhydride or the like. Furthermore, among the compounds V!, compoundswhose X is F can be produced by using a compound derived fromperfluoroethyleneoxide oligomer as a starting compound and the compoundsVI! can be produced by using a compound derived fromdifluorooxymethylene oligomer as a starting compound, each followed byapplying thereto the same terminal nitrilation reaction as describedabove.

Inevitably, the thus obtained dinitrile compounds contain mononitrilecompounds as by-products. It is possible to suppress formation ofmononitrile compounds by using starting materials, catalyst, solvent,etc. having a very high purity and conducting the reaction underrestricted conditions, and dinitrile compounds having a high purity canbe produced thereby. However, the production cost is considerablyincreased.

In the present invention, dinitrile compounds having a relatively lowmolecular weight can be used and thus starting materials and by-productscan be readily separated therefrom by an appropriate purification meanssuch as distillation, etc. and dinitrile compounds having a purity of95% or more can be usually obtained. It is not particularly difficult toobtain a dinitrile compound having a purity of 98% or more. Numberaverage molecular weight and bifunctional purity of dinitrile compoundcan be conveniently determined by ¹³ F-NMR spectrum analysis.

Reaction of dinitrile compound with ammonia is carried out by carefullyadding a dinitrile compound dropwise to generally at least 5 parts bymole, preferably 20 parts by mole, of ammonia per part by mole of thedinitrile compound with stirring. In case of using less than 5 parts bymole of ammonia, the reaction to form amizine groups is retarded andother side reactions occur considerably.

Generally, liquid ammonia is used as ammonia. Gaseous ammonia can bealso used, where it is preferable to conduct the reaction under pressureby making the partial pressure of ammonia as high as possible. It isalso possible to conduct the reaction while keeping ammonia in solutionin a solvent, where ether-based solvents such as diethylether,tetrahydrofuran, etc.; hydrocarbon-based solvents such as cyclohexane,octane, toluene, etc., and chlorine-based solvents such asdichloromethane, dichloroethane, etc. can be used as the solvent.Fluorine-based solvents such as trichlorotrifluoroethane,perfluorohexane, perfluoroethane, perfluoro(2-butyltetrahydrofuran),2H-tetradecafluoro-5-(trifluoromethyl)-3,6-dioxanonane,perfluorotributylamine, etc. or mixtures containing these solvents areparticulary preferable owing to their high solubility of the respectivestarting materials.

Reaction temperature is in a range of about -90° C. to about +70° C.,preferably about -70° C. to about +50° C. Below about -90° C., nosubstantial reaction rate can be obtained, whereas above about +70° C.,the vapor pressure of ammonia is so high that reaction operations arehard to obtain. When the reaction temperature is below -33° C., boilingpoint of ammonia, any pressure vessel is not required for the reaction,whereas at a reaction temperature of -33° C. or higher, it is preferableto use a pressure vessel for the reaction. However, when afluorine-based solvent having a good ammonia solubility, it is notalways necessary to use a pressure vessel even at or above -33° C., buteven in that case it is desirable to conduct the reaction in a pressurevessel at a high ammonia concentration condition.

As a result of reaction of dinitrile compound with ammonia, a reactionproduct containing a diamizine compound I! having amizine groupsconverted from nitrile groups as the main component can be obtained. Ithas been confirmed by ¹³ F-NMR spectrum analysis that a small amount ofother terminal functional groups than the amizine groups are formed atthe same time, but the reaction product itself can be used in thesuccessive reaction. Since the nitrile groups of dinitrile compound havecharacteristic absorption at 2,260 cm⁻¹, whereas the amizine groups havea characteristic absorption at 1,695 cm⁻¹, the degree of reactionprogress can be readily detected by changes in these peak intensities.

The resulting diamizine compound has n=0.01˜4 in said formula I!.

Second step

The diamizine compound I! obtained in the first step is furthersubjected to reaction with a dinitrile compound represented by thegeneral formula NC--Rf¹ --CN to obtainperfluoroalkyleneetherpolyimidoylamizine oligomer II! represented by thefollowing general formula: ##STR3##

This reaction to polymerize the diamizine compound I! is carried outunder the substantially same conditions as in the first step, and inthat case the diamizine compound must be used at least in an equimolaramount to the dinitrile compound. When more dinitrile compound is used,the CN groups will remain at the molecule terminals of the resultingperfluoroalkyleneetherpolyimidoylamizine oligomer II!, which will givean adverse effect to the reaction to treat the terminal groups to becarried out in the successive third step.

The degree of the third step reaction can be detected by measurement ofinfrared absorption spectrum or viscosity. As to the measurement ofviscosity it is reported that there is a linear relationship between theweight average molecular weight by GPC of the oligomer and that ofpolytriazine derived therefrom J. of Polymer Sci.; Polymer letters Ed.Vol. 18, page 135, (1980); Ind. Eng. Chem.; Product researchdevelopment, Vol. 20, page 694 (1981); U.S. Pat. No. 4.242,498!.

The process for producing perfluoroalkyleneetherpolyimidoylamizineoligomer based on the foregoing first and second steps can produce theproduct up to a considerable degree of polymerization by the two-stagepolymerization procedure from a readily available dinitrile compound ofrelatively low molecular weight as a starting material.

Third step

The perfluoroalkyleneetherpolyimidoylamizine obtained in the second stepis further subjected to reaction with a perfluoronitrile compoundrepresented by the general formula Rf² CN to obtain terminalgroup-treated perfluoroalkyleneetherpolyimidoylamizine oligomer III!represented by the following general formula: ##STR4##

The perfluoronitrile compound for use in the present invention includescompounds VII! whose Rf² is a perfluoroalkyl group, for example, CF₃ CN,C₂ F₅ CN, C₃ F₇ CN, C₆ F₁₃ CN and C₆ F₁₇ CN; compounds VIII! whose Rf²is CF₃ (OCF₂)e--, for example, CF₃ (OCF₂)₆ CN, CF₃ (OCF₂)₈ CN and CF₃(OCF₂)₉ CN; and compounds IX! whose Rf² is RfO(CFXCF₂ O)kCFX--, forexample, CF₃ OCF₂ CF₂ OCF₂ CN, CF₃ O(CF₂ CF₂ O)₂ CF₂ CN, C₃ F₇ O(CF₂ CF₂O)₃ CF₂ CN, CH₃ OCF(CF₃)CF₂ OCF (CF₃)CN, CH₃ O CF(CF₃)CF₂ O!₂ CF(CF₃)CN,CH₃ O CF(CF₃)CF₂ O!₃ CF (CF₃)CN, C₃ F₇ OCF(CF₃)CF₃ CF(CF₃)CN, C₃ F₇ OCF(CF₃)CF₂ O!₂ CF(CF₃)CN and C₃ F₇ O CF(CF₃)CF₂ O₃ !CF(CF₃)CN.

The perfluoronitrile compound is usually used by about 10 to about 20%by mole in excess of the perfluoroalkyleneetherpolyimidoylamizineoligomer and the conditions for the third step reaction aresubstantially the same as those for the first step reaction.

Fourth step

The terminal group-treated perfluoroalkyleneetherpolyimidoylamizineoligomer III! obtained in the third step is further subjected to aring-closing reaction with a perfluoroacylating agent represented by thegeneral formula Rf³ COY, where Y is a halogen atom, to obtain thedesired perfluoroalkyleneethertriazine oligomer IV!.

The perfluoroacylating agent for use in the present invention includes,for example, CF₃ (OCF₂)₅ COF, CF₃ (OCF₂)₆ COF, CF₃ (OCF₂)₇ COF, CF₃(OCF₂)₈ COF, CF₃ (OCF₂)₉ COF, C₂ F₅ (OCF₂)₈ COF, C₃ F₇ (OCF₂)₅ COF andCF₃ OCF(CF₃)!₃ COF. The ring-closing reaction with theperfluoroacelating agent is usually carried out in the presence of atertiary amine such as pyridine, aromatic amines, etc.

After the end of reaction, the resulting reaction product is added tochloroform, and the chloroform-insoluble layer is separated therefrom.An oxygen-containing gas, preferably air, is blown into the remainingliquid compound at about 250° to about 350° C., preferably about 300° toabout 320° C. to remove impurities therefrom. Then, the resulting liquidcompound is subjected to purification (decolorization and clarifying)with an adsorbent such as activated carbon, silica, alumina, etc.,preferably wet process silica.

The resulting perfluoroalkyleneethertriazine oligomer IV! is added toperfluoropolyether having a viscosity of about 10 to about 500 Cst at40° C., represented by anyone of the following general formula (a), (b),(c) and (d):

(a) Rf⁴ O(CFXC₂ O)pRF⁵ wherein Rf⁴ and Rf⁵ are perfluoro(lower alkyl)groups; X is a fluorine atom or a CF₃ group; and p is an integer of 10to 100,

(b) Rf⁴ O(CF₂ CF₂ CF₂ O)pRF⁵ wherein Rf⁴, Rf³ and p have the samemeanings as defined above,

(c) Rf⁶ O(CFXCF₂ O)q(CF₂ O)rRf⁷ wherein Rf⁶ and Rf⁷ are perfluoro(loweralkyl) groups; X has the same meaning as defined above; q is 99.9 to 90;and r is 0.1 to 10, and

(d) Rf⁶ O(CF₂ CF₂ O)s(CF₂ O)tRf⁷ wherein Rf⁶, Rf⁷ have the same meaningsas defined above; s is 90 to 30 and t is 20 to 3, where s/t is(90˜80)/(10˜20), and can form an oily composition with an improved heatresistance. In that case, about 20 to about 5 parts by weight ofperfluoroalkyleneethertriazine oligomer IV! is added to about 80 toabout 95 parts by weight of oil consisting of perfluoropolyether.

Furthermore, a greasy composition with an improved heat resistance canbe obtained by adding about 5 to about 60 parts by weight, preferablyabout 15 to about 45 parts by weight, of polytetrafluoroethylene powderto 100 parts by weight of the above oily composition.

The present invention provides a perfluoroalkyleneethertriazine oligomerhaving a good resistance to oxidation at a high temperature,particularly at a high temperature in the presence of a metal, and canimprove the heat resistance of a perfluoropolyether-based oil or aperfluoropolyetherpolytetrafluoroethylene powder-based grease, whenadded thereto. Furthermore, the present perfluoroalkyleneethertriazineoligomer is also distinguished in the cryogenic resistance, since it hasperfluoropolyether groups at the side chains.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will be described in detail below, referring toExamples.

EXAMPLE 1

(1) Synthesis of diamizine compound:

A flask having a capacity of 0.25 liters, provided with a granularKOH-filled, ammonia inlet tube, a stirrer, a thermometer and a refluxcondenser (dry ice/ethanol) was cooled over a dry ice/ethanol bath, andthen 39.1 g (2.3 moles) of dry ammonia was introduced therein throughthe ammonia inlet tube. After the above-mentioned amount of the ammoniaas liquefied was introduced into the flask, the ammonia inlet tube wasreplaced with a dropping funnel, and 50 g (0.115 moles) of dinitrilecompound having the following formula:

    NCCF(CF.sub.3)O(CF.sub.2).sub.3 OCF(CF.sub.3)CFCN

was carefully dropwise added thereto with stirring, while maintainingthe inside temperature at -60° C. to -70° C. After the dropwiseaddition, stirring was further continued for 0.5 hours at thattemperature.

Then, the reaction system was brought back to the ordinary temperatureand the atmospheric pressure, and unreacted ammmonia gas was purgedtherefrom, and then the reaction system was heated at 40° C. underreduced pressure (about 1 to 3 mmHg) for about 6 hours, whereby 48.0 gof diamizine compound having a molecular weight of 766 ( η!=0.66) andthe following structural formula was obtained (yield: 54.5%). ##STR5##

(2) Synthesis of perfluoroalkyleneetherpolyimidoylamizine oliopmer:

46.3 g (0.06 moles) of the thus obtained diamizine compound and 21.6 g(0.05 moles) of the same dinitrile compound as used above (1) werecharged into a 4-necked flask having a capacity of 200 ml, provided witha stirrer, a thermometer, a reflux condenser and an inert gas lineconnection, and stirred for 6 hours, while maintaining the flask at atemperature of 25° to 30° C., whereby 68 g ofperfluoroalkyleneetherpolyimidoylamizine oligomer having a molecularweight of 11,450 (by isoplestic measurement in perfluorobenzene, as willbe here after used for the measurement of molecular weight) was obtained(yield: 99%).

(3) Synthesis of terminal group-treatedperfluoroalkyleneetherpolyimidoylamizine oligomer:

8.9 g (0.019 moles) of CF₃ (CF₂)₅ CN was added to theperfluoroalkyleneetherpolyimidoylamizine oligomer obtained in (2) andthe mixture was stirred for 3 hours, while keeping the flask at atemperature of 25° to 30° C., whereby 72.1 g of the terminalgroups-stabilized perfluoroalkyleneetherpolyimidoylamizine oligomerhaving a molecular weight of 12,140 was obtained (yield: 99.8%).

(4) Synthesis of perfluoroalkyleneethertriazine oligomer:

40.9 g (0.518 moles) of dry pyridine, 100 ml of dry Freon 113 and 195.7g (0.382 moles) of CF₃ (OCF₂)₆ COF were charged into a 5-necked flaskhaving a capacity of 500 ml, provided with a stirrer, a reflux cooler, athermometer, a dropping funnel and an inert gas inlet tube, and then72.1 g (0.16 moles) of the terminal group-treatedperfluoroalkyleneetherpolyimidoylamizine oligomer obtained in (3) anddissolved in dry Fron was dropwise added thereto with stirring. Afterthe dropwise addition, stirring was further continued for 6 hours, whilekeeping the flask at a temperature of 40° to 45° C. After the reactionmixture was cooled, 300 ml of chloroform was added thereto, and theresulting chloroform-insoluble layer was separated. The separated layerwas washed three times with 200 ml of chloroform.

The resulting liquid compound was transferred into a flask connected toa receptacle, and dry air was bubbled in the flask for 12 hours, whileheating the flask at a temperature of 300° to 310° C. After the cooling,the liquid compound was placed on a filter under pressure, and 8.0 g ofwet process silica was added thereto with stirring. The mixture wasfiltered through a filter paper under pressure, whereby 105.0 g ofliquid perfluoroalkyleneethertriazine oligomer having a molecular weightof 23,700 was obtained (yield: 69.5%).

Kinematic viscosity (50° C.): 262 mm² /sec.

Solidification point: -40° C.

Heating loss (in air at 300° C. for 31 hours): 13.2%

EXAMPLES 2 to 14

Perfluoroalkyleneethertriazine oligomers represented by the followinggeneral formula: ##STR6## were produced through a series of the samesteps as in Example 1.

In the foregoing general formula, groups Rf⁰, Rf¹, Rf² and Rf³ are shownin the following Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Ex. No.                                                                           Rf.sup.0  Rf.sup.1 Rf.sup.2  Rf.sup.3                                     __________________________________________________________________________    1   (A)CF.sub.2 (B)                                                                         (A)CF.sub.2 (B)                                                                        C.sub.6 F.sub.13                                                                        CF.sub.3 (OCF.sub.2).sub.6                   2   (A).sub.3 CF.sub.2 (B).sub.2                                                            (A).sub.3 CF.sub.2 (B).sub.2                                                           "         CF.sub.3 (OCF.sub.2).sub.6.5                 3   "         "        "         CF.sub.3 (OCF.sub.2).sub.8.2                 4   "         (CF.sub.2).sub.6                                                                       "         CF.sub.3 (OCF.sub.2).sub.6                   5   "         "        "         "                                            6   "         (A)CF.sub.2 (B)                                                                        "         "                                            7   (A).sub.2 CF.sub.2 (B).sub.2                                                            (A).sub.2 CF.sub.2 (B).sub.2                                                           CF.sub.3 (OCF.sub.2).sub.3                                                              CF.sub.3 (OCF).sub.8.7                       8   "         "        "         CF.sub.3 (OCF.sub.2).sub.8                   9   "         "        "         CF.sub.3 (OCF.sub.2).sub.9                   10  "         "        CF.sub.3 (OCF.sub.2).sub.8.5                                                            CF.sub.3 (OCF.sub.2).sub.8                   11  (A)CF.sub.2 (B)                                                                         (A)CF.sub.2 (B)                                                                        CF.sub.3 (OCF.sub.2).sub.6                                                              CF.sub.3 (OCF.sub.2).sub.6                   12  "         "        "         "                                            13  (A).sub.2 CF.sub.2 (B)                                                                  "        CF.sub.3 (OCF.sub.2).sub.9                                                              CF.sub.3 (OCF.sub.2).sub.7                   14  "         "        CF.sub.3 (OCF.sub.2).sub.8                                                              CF.sub.3 (OCF.sub.2).sub.8                   __________________________________________________________________________     Remarks:                                                                      ##STR7##                                                                     -  -                                                                           ##STR8##                                                                 

The liquid perfluoroalkyleneethertriazine oligomers obtained in Examples2 to 14 were measured for the following properties:

    ______________________________________                                        n value:  (diamizine MW - Rf.sup.0 dinitrile Mw - 34)/                                  (Rf.sup.0 dinitrile MW + 17)                                        m value:   (oligomer MW) - (n + 1)(Rf.sup.1 dinitrile MW) -                             (n + 2)(Rf.sup.3 COY MW - 21) - 2(Rf.sup.2 dinitrile MW)!/                     (n + 1)(Rf.sup.1 dinitrile MW) + (Rf.sup.0 dinitrile MW) +                   (n + 2)(Rf.sup.3 COY MW - 21)!                                      ______________________________________                                    

Diamine/dinitrile ratio (DA/DN ratio)

Found number average molecular weight (found Mn)

Yield (%)

Kinematic viscosity (50° C., mm² /sec.): by Canon-Fenske viscometer

Solidification point (°C.)

Amount of volatile matters by heating in air (% by weight): heating at300° C. for one hour, 300° C. for 31 hours and 350° C. for one hour

Heating loss (% by weight): heating at 300° C. for 620 hours, 800 hoursor 1,000 hours.

The results are showing in the following Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Properties\Example No.                                                          1    2    3    4    5    6    7                                   __________________________________________________________________________    n value     0.625                                                                              0.098                                                                              0.098                                                                              0.210                                                                              0.210                                                                              0.210                                                                              0.237                               m value     9.81 9.06 9.87 4.34 5.53 6.05 1.81                                DA/DN ratio 1.125                                                                              1.125                                                                              1.125                                                                              1.333                                                                              1.333                                                                              1.333                                                                              1.500                               Found Mn    23700                                                                              28400                                                                              32200                                                                              11630                                                                              14290                                                                              16130                                                                              8600                                Yield       70.0 75.5 74.8 78.0 82.0 71.9 81.2                                Kinematic viscosity                                                                       262  1098 888  143  285  509  58                                  Solidification point                                                                      -40  -35  -40  -52  -48  -49  -67                                 Amount of volatile matters                                                    300° C.-1 hr                                                                       5.6  4.1  0.8  22.8 19.7 17.3 28.4                                300° C.-31 hrs                                                                     15.0 10.0 7.2                 56.5                                350° C.-1 hr                                                                       14.3 7.8  5.6                                                     Heating loss                                                                   620 hrs                                                                       800 hrs                                  41.6                                1000 hrs    9.9  6.3  3.6  28.9 17.6 9.9                                      __________________________________________________________________________    Properties\Example No.                                                          8    9    10   11   12   13   14                                  __________________________________________________________________________    n value     0.237                                                                              0.237                                                                              7.310                                                                              0.082                                                                              0.082                                                                              0.070                                                                              0.120                               m value     2.60 4.00 0.16 3.41 5.29 2.86 5.35                                DA/DN ratio 1.333                                                                              1.250                                                                              --   1.500                                                                              1.200                                                                              1.220                                                                              1.220                               Found Mn    11000                                                                              15800                                                                              14500                                                                              8140 11360                                                                              9070 12690                               Yield       75.4 86.0 83.0 67.0 71.6 74.0 71.0                                Kinematic viscosity                                                                       125  108  129  57   110  88   138                                 Solidification point                                                                      -58  -67  -63  -68  -60  -72  -61                                 Amount of volatile matters                                                    300° C.-1 hr                                                                       20.3 10.7 17.3 34.4 20.6 20.8 12.6                                300° C.-31 hr                                                                      38.3 29.0 32.4 52.6 32.7 48.6 33.6                                350° C.-1 hr                                                           Heating loss                                                                   620 hrs                             5.8  4.3                                  800 hrs    30.7 18.5 23.4                                                    1000 hrs                   30.6 22.0                                          __________________________________________________________________________

To 50 g of the perfluoroalkyleneethertriazine oligomer obtained inExample 3 were added the following materials:

C₃ F₇ O CF(CF₃)CF₂ O!q(CF₂ O)rCF₃ : 620 g

q:r=97:3

viscosity: 330 mm² /sec. (40° C.)

Polytetrafluoroethylene powder: 330 g

Then, the mixture was stirred in a stirring vessel for one hour andkneaded through rolls at three stages to obtain a greasy mixture A!.

Separately, a greasy composition B! was prepared from 670 g of theabove-mentioned perfluoropolyether and 330 g of thepolytetrafluoroethylene powder without using theperfluoroalkyleneethertriazine oligomer.

These greasy compositions were measured for the following properties andthe results are shown in the following Table 3.

Liquation consistency: according to JIS K-2220

Evaporation amount: weight loss of greasy composition, when 0.6 g ofgreasy composition was uniformly applied to an aluminum dish, having 35mm in diameter and 5 mm deep, followed by heating at 300° C. for 5hours, 50 hours or 300 hours

                  TABLE 3                                                         ______________________________________                                                  Liquation                                                                             Evaporation amount (wt. %)                                  Greasy composition                                                                        consistency                                                                             5 hrs    50 hrs                                                                              300 hrs                                  ______________________________________                                        A           270       5.3      9.2   13.7                                     B           265       25.9     55.2  60.4                                     ______________________________________                                    

It is obvious from Table 3 that the present greasy composition has agood stability against oxidation at a high temperature even in thepresence of a metal.

EXAMPLE 15 to 29

Other perfluoroalkyleneethertriazine oligomers having the followinggeneral formula were synthesized through a series of he same steps as inExample 1. ##STR9##

In the general formula, groups Rf⁰, Rf¹, Rf² and Rf³ are shown in thefollowing Table 4.

                  TABLE 4                                                         ______________________________________                                        Ex. No.                                                                             Rf.sup.0, Rf.sup.1                                                                            Rf.sup.2   Rf.sup.3                                     ______________________________________                                        15    (A).sub.3 CF.sub.2 (B).sub.3                                                                  C.sub.3 F.sub.7 O(D)                                                                     CF.sub.3 (OCH.sub.2).sub.6                   16    "               CF.sub.3 (OCH.sub.2).sub.8                                                               "                                            17    "               "          "                                            18    "               C.sub.3 F.sub.7 O(D)                                                                     CF.sub.3 (OCF.sub.2).sub.8                   19    "               "          "                                            20    "               CF.sub.3 (OCF.sub.2).sub.8                                                               "                                            21    (A)CF.sub.2 (B) C.sub.3 F.sub.7 O(D)                                                                     CF.sub.3 (OCF.sub.2).sub.6                   22    "               "          "                                            23    "               CF.sub.3 (OCF.sub.2).sub.8                                                               "                                            24    "               C.sub.3 F.sub.7 O(D)                                                                     CF.sub.3 (OCF.sub.2).sub.8                   25    "               "          "                                            26    "               CF.sub.3 (OCF.sub.2).sub.8                                                               "                                            27    CF.sub.2 O(CF.sub.2 O).sub.6 CF.sub.2                                                         "          "                                            28    "               "          "                                            29    "               "          "                                            ______________________________________                                         Remarks:                                                                      ##STR10##                                                                    -  -                                                                           ##STR11##                                                                    -  -                                                                           ##STR12##                                                                

The liquid perfluoroalkyleneethertriazine oligomers obtained in Examples1 to 29 had properties given in the following Table 5.

                  TABLE 5                                                         ______________________________________                                        Ex. No.                                                                             Found Mn   Kinematic viscosity                                                                        Solidification point                            ______________________________________                                        15    10606      525          -35                                             16    8330       139          -55                                             17    15450      598          -41                                             18    8930       173          -54                                             19    15850      712          -44                                             20    10300      107          -65                                             21    8750       143          -53                                             22    13090      306          -50                                             23    11310      140          -65                                             24    9435       102          -63                                             25    12680      186          -61                                             26    10090      93           -77                                             27    9000       --           -97                                             28    10000      --           -94                                             29    12000      --           -90                                             ______________________________________                                    

EXAMPLE 30

(1) About 0.3 g of perfluoroalkyleneethertriazine oligomer obtained inExample 3 was placed on an aluminum dish, having 30 mm in diameter and 7mm deep, and then exactly weighted. Then, the dish was placed in an ovenat 300° C. After 5 hours, weight loss was measured. It was found to be3. 93%.

(2) Weight loss of CF₃ O CF(CF₃)CF₂ O!q(CF₂ O)rC₂ F₅, where q:r=98:2;viscosity: 150 mm² /sec. (40° C.) and 45 mm² /sec. (100° C.); andsolidification point: -70° C., was measured in the same manner as in (1)and was found to be 85.1%.

(3) Weight loss of an oily mixture consisting of 95 parts by weight ofthe same perfluoropolyether ae used in (2) and 5 parts by weight of thesame perfluoroalkyleneethertriazine oligomer as used in (1) was likewisemeasured and found to be 2.57%.

As is evident from the above, the present perfluoroalkyleneethertriazineoligomer can effectively prevent decomposition due to a metal, as oftenobserved in case of perfluoropolyether.

What is claimed is:
 1. A process for producing aperfluoroalkyleneethertriazine oligomer represented by the followinggeneral formula: ##STR13## wherein Rf⁰ is --(CFXOCF₂)a(CF₂)b(CF₂OCFX)c--, where X is a fluorine atom or a CF₃ group, a is an integer of1 to 5, b is an integer of 1 to 2 and c is an integer of 1 to 5, or Rf⁰is --CF₂ O(CF₂ O)dCF₂ --, where d is an integer of 1 to 8; Rf¹ has thesame meaning as that for Rf⁰ or Rf¹ is a perfluoroalkylene group having4 to 8 carbon atoms; Rf² is CF₃ (OCF₂)_(e) -- where e is an integer of 3to 10; and Rf³ is CF₃ (OCF₂)₁, where f is an integer of 3 to 10 and n is0.01 to 10 and m is 0.01 to 20, which comprises subjecting a terminallytreated perfluoroalkyleneetherpolyimidoylamizine oligomer represented bythe following general formula: ##STR14## wherein Rf⁰, Rf¹, Rf², n and mhave the same meanings as above, to a ring-closing reaction with aperfluoroacylating agent represented by the general formula: Rf³ COY,wherein Rf³ has the same meaning as defined above, and Y is a halogenatom.
 2. A process according to claim 1, wherein an oxygen-containinggas is blown into the resulting ring-closing reaction product at about250° C. to about 350° C., thereby removing impurities therefrom,followed by purification treatment in the presence of a adsorbent.
 3. Aprocess according to claim 2, wherein the adsorbent is wet processedsilica.